(a) Technical Field
The present invention relates to a dark current cutoff system and method for a vehicle junction box. More particularly, the present invention relates to a dark current cutoff system and method for a vehicle junction box, in which the vehicle junction box cuts off a dark current consumed by a load device after powering down, thereby minimizing the battery discharge problem caused by the dark current.
(b) Background
A vehicle typically utilizes a junction box for supplying battery power to various electronic devices consuming electricity in the vehicle, such as lamps, body electrical/electronic parts, multimedia devices, motor driving devices, etc. In this junction box are installed relays for opening and closing a plurality of fuses or power supply to prevent delivery of overcurrent or overload to an external circuit.
The junction box mainly supplies and distributes battery power, wire protection, and so forth, and also functions as a housing and protection for various other related elements (e.g., fuses, relays, etc.) mounted thereon, operation efficiency maintenance through rapid heat emission, etc.
Since various electrical devices using battery power are connected in the junction box, a technique for cutting off “dark current” consumed by those electrical devices is often applied to a junction box. “Dark current” refers to current consumed by various load devices which use battery power even after the vehicle has been powered off. Once a certain amount of time has elapsed from production of the vehicle until delivery of the vehicle to a customer or the vehicle has not been operated for a long time due to export, long-term storage, parking, or the like, the battery may become discharged due to dark current flows through a load device using B+ power of the vehicle at all times (i.e., even when the vehicle is turned off).
To solve this problem, a dark current cutoff device for cutting off a power supply path between a battery and a load device until delivery to a customer is typically used in a junction box, and an example of this scheme is the application of a power connector.
That is, a power connector connected with a fuse may be installed in the junction box which is disposed between the battery and the load device; when the power connector is connected with the junction box, battery power can be provided to the load device, but when the power connector is disconnected, the power supply path to the load device is cut off. Thus, the power connector is disconnected until delivery of the vehicle to the customer (or by a driver if the vehicle is not going to be used for a long time), thus minimizing the battery discharge caused by dark current.
This power connector, however, is difficult to manipulate, and therefore as a result a Smart Junction Box (SJB) has been developed. IN the SJB, a dark current cut off device (power cut device) cutting off battery discharge caused by dark current is applied using a mode switch and a switching element. Such a scheme solves a problem of an existing power connector which manually cuts off battery power and dark current, such that if a mode switch is turned off until delivery of the vehicle to the customer at an export or dealer stage the power supply path is cut off like in the disconnection of the power connector.
On the other hand, when the vehicle is delivered to the customer, the mode switch is turned on, such that the battery power can be normally provided to the load device in the vehicle. When the SJB is applied, even if the mode switch is turned off, the power cut state is released upon opening of the vehicle door or startup by a dealer and the battery power is normally connected to the load device.
In the SJB to which the mode switch is applied, even when a driver mistakenly leaves the interior lights on, a door half-closed, a hood open, a trunk open, etc., The power to the indoor lamps is automatically cut off after a predetermined time, thus preventing discharge.
In the SJB, a controller in the SJB is connected with other modules in the vehicle, such as a body control module (BCM), a driver door module (DDM), and so forth, in a way to enable controller area network (CAN) communication (B-CAN communication) therewith. Thus, the controller checks mode states of other modules in the vehicle, i.e., a sleep mode or a wakeup mode state, to perform a power cutting operation for cutting off dark current to a load device or a power cut release operation for enabling power supply accordingly.
The controller in the SJB turns on/off a switching element, such as a relay, for opening and closing power to the load device during the power cut or release operation, thus cutting off the power supply path to the load device (i.e., cutting off the battery power and dark current) or activating the power supply path for supplying power (releasing the power cut).
The controller, upon recognizing that each of a plurality of modules in the vehicle have entered sleep mode, turns off the switching element to cut off the battery power to the load device. In this case, if any signal is not input from other modules in the vehicle through CAN communication, the controller recognizes that such modules are in the sleep mode, and in the sleep mode, the controller cuts off the battery power by turning off the switching element connected to the load device after a predetermined time.
If the door of the vehicle is opened or accessory devices of other modules in the vehicle operate, the mode states of the modules are switched to the wakeup mode, and at this time, once the controller receives a signal indicating that the controller should switch to the wakeup mode from the modules through CAN communication, the controller performs a power cut release operation to turn on the switching element to supply the battery power to the load device again.
However, in the foregoing dark current cutoff scheme, normal dark current cut off may not be achieved due to noise generated at a moment when the power is cut off by turning off the switching element after the sleep mode of other modules of the vehicle in the junction box is recognized. That is, even when the controller of the junction box recognizes that all the modules in the vehicle are in the sleep mode and thus turns off the switching element, an arbitrary noise signal (abnormal CAN signal) may be input to the controller of the junction box from a module through a CAN communication module due to a capacitor component of a circuit in the module such as an amplifier.
In this case, the controller incorrectly recognizes that the module has been switched to the wakeup mode. As a result, the switching element is turned on, the power is reconnected (power cut release), and actual switching to the wakeup mode is established. As a result, even when the controller of the junction box recognizes the sleep mode of the module again and then performs the power cut operation by turning off the switching element, if a wrong CAN signal is input to the controller within a delay time in which a capacitor component is discharged from a particular module in the vehicle, the same malfunction may repetitively occur, thereby resulting in fully discharged battery.